The voters also snatched two rifles from the security personnel. People pelted stones at the security personnel and attacked poll equipment.
Balloting was stopped in five polling booths in and around the area immediately after the incident.
"Someone spread rumours at the polling station in Balipara L.P. School, located 25 km from Kokrajhar, that the EVMs were not functioning properly. But it turned out to be a rumour. However, the voters turned violent and attacked the security personnel," said Additional Director General of Police A.P. Raut.
One police constable was killed, while two others who tried to control the situation were seriously injured in the mob violence, Raut said.
A total of 2,049 polling stations were set up in Kokrajhar Lok Sabha constituency and 130 of them were identified as "very sensitive". Over 20 companies of security forces were deployed in Kokrajhar to ensure smooth polling.
Polling is being held Thursday in six Lok Sabha constituencies in the last of three-phased balloting for a total 14 seats from the state.